Rock drill bit



' i 4, 1953 R. T. EAKIN 2,634,954

ROCK DRILL BIT Filed June 19, 1948 dZZorzzey Patented Apr. 14, 1953 UNITED STATES PATENT OFFICE ROCK DRILL BIT Robert T. Eakin, Ferndale, Mich., assignor to Joy Manufacturing Company, Pittsburgh, Pa., a corporation of Pennsylvania.

Application June 19, 1948, Serial No. 34,112

8 Claims. (01. 255-64) This invention relates to rock drill bits and more particularly to rock drill bits of the impact type having hard metal inserts set in the cutting face to provide wear resisting cutting edges.

In rock drill bits of the impact type, it has recently become common practice to secure hard metal inserts, usually of tungsten carbide, in slots cut in the front face of the bit body to provide wear resisting cutting edges. In bits of such character, considerable difficulty has been encountered in manufacture and particularly in securing the hard metal inserts against endwise displacement in the slots toward the bit center under the terrific impact action during use of the bit, such inward displacement often resulting in direct contact of the tungsten carbide inserts and frequent breakage. Moreover, movement of the inserts into the center of the bit causes obstruction of the flow of cleansing fluid to the cutting face of the bit. The present invention contemplates improvements over known types of rock drill bits having hard metal inserts in that novel structure is provided at the bit center for precluding endwise displacement of the hard metal inserts in the slots toward the bit center while providing unimpeded flow of cleansing fluid to the cutting face of the bit.

An object of the present invention is to provide an improved rock drill bit. Another object is to provide an improved rock drill bit of the impact type having hard metal inserts set in the cutting face of the bit to provide wear resisting cutting edges. Another object is to provide an improved rock drill bit of the impact type having slots cut in the front face of the bit body to receive hard metal inserts which are secured in position in the object is to provide an improved abutment means arranged centrally of the bit to prevent inward displacement of the inserts in the slots toward the bit center and so arranged and constructed as to permit free flow of cleansing fluid from the central bit passage to the cutting face of the bit. A still further object is to provide an improved centrally located abutment means of generally cruciform shape, herein in the form of a spider or cross member, the arms of which provide abutments for the hard metal inserts to prevent inward displacement thereof in the slots in the bit face toward the center of the bit and providing ample fiow passages between the spider or cross arms for the free flow of cleansing fluid to the cutting face of the bit. These and other objects and advantages of the invention will, however, hereinafter more fully appear.

In th accompanying drawing there are shown for purposes of illustration one form and a modification which the invention may assume in practies.

In this drawing:

Fig. 1 is a central longitudinal sectional View through a drill bit constructed inaccordance with a preferred illustrative embodiment of the invention.

Fig. 2 is a cross-sectional view taken on line 22 of Fig. l.

Fig. 3 is a front end view of the drill bit.

Fig. 4 is a central longitudinal sectional view taken on line 4-4 of Fig. 2.

Fig. 5 is a perspective view of the central abutment spider.

Fig. 6 is a perspective view of one of the hard metal inserts.

Fig. '7 is a perspective view of the drill bit, looking toward the cutting face.

Fig. 8 is a fragmentary central longitudinal sectional view illustrating a modified construction.

In this illustrative construction, as shown in the drawing, the rock drill bit, generally designated l, comprises a body 2 shaped, as by forging, with a forward portion of generally cruciform shape providing cross wings 3. The bit body tapers slightly rearwardly and has an integral rearward stud 4 adapted for attachment to a conventional socketed drill rod.

The cross wings 3 are centrally slotted at 5 along diametric lines, with the slots in substantially right angular relation, and at the center of the bit, the slots cut into a central recess 6 in the front side of the bit body. The bit body and stud have a usual axial cleansing fluid passage 1 which communicates with the central recess. 6. In this improved construction, the slots 5 are cut into the front face of the bit body to a depth substantially below the bottom of the central recess 6, as shown in Figs. 1 and 2. Seated in the slots are hard metal inserts 8, preferably of tungsten carbide, providing wear resisting cutting edges 9 and secured in position in the slots as by brazing. The outer ends of the inserts lie substantially flush with the outer periphery of the bit, and the inner ends of the inserts preferably terminate at the side walls of the central recess 6, as shown in Figs. 1 and 3, with the inner ends spaced from the bit center. As shown in Fig. 6, the hard metal inserts are generally rectangular in shape and are relatively thin, and the slots cut in the bit face, as shown in Fig. 2, are relatively narrow to provide a tight fit for the inserts. Evidently, the hard metal inserts may be made wider or thicker in cross section, with a corresponding increase in the width of the slots, if desired.

Now referring to the improved abutment means generally designated H] for preventing inward displacement of the hard metal inserts in the slots toward the bit center, it will be noted that arranged in the bit body inwardly of the central recess 6 and secured to the bit body, as by brazing, with portions received in the slots 5, is a generally cruciform shaped abutment element ll, herein in the form of a spider or cross member, preferably made of steel. The spider has rectangularly related arms l2 secured as by brazing in the inner portions of the slots and providing abutment surfaces at 3 with which the inner ends of the inserts abut. The top surface of the spider preferably lies flush with the bottom surface of the central recess 6, as shown. Between the arms of the spider are spaces 14 which permit free flow of cleansing fiui'd past the spider to the central recess 6 while providing a comparatively rigid central abutment structure for the inserts. Formed in the front face of the bit body are radial recesses [5 which communicate with the central recess ii intermediate the inserts, and these recesses communicate with grooves r recesses it on the exterior of the bit body between the wings 3. Thus while attaining a rigid central abutment for the inserts, cleansing fluid may flow freely from the central recess through the recesses i transversely of the bit face and rearwardly through the side recesses or grooves 16.

Evidently, the central abutment may be located and supported at the center of the bit in other manners. For example, the central recess 6 may extend to the bottoms of the slots as shown in Fig. 8, with the bottom of the spider l0 secured, as by brazing, at H, to the bottom of the recess. In that event, the central passage could be slightly enlarged, as by flaring or tapering at E8, where it communicates with the bottom of the central recess to increase the flow passage area and to direct the fluid to the spaces between the spider arms. lhe securing of the spider arms in the slots 5 in the manner shown provides, however, an extremely rigid manner of support.

As a result of this invention, an improved rock drill bit is provided having hard metal inserts set in slots in the bit face to provide wear resisting cutting edges. By the provision of the improved central abutment structure, the possibility of endwise displacement of the hard metal inserts in the slots toward the bit center is avoided. The novel spider or cross abutment element not only provides a rigid abutment structure for preventing inward displacement of the inserts, but also provides for free flow of cleansing fiuid from the central bit passage to the cutting face of the bit. The novel abutment structure not only provides a rigid central abutment and free fiuid fiow, but also is simple and rugged in design. Gther advantages of the invention will be clearly apparent to those skilled in the While there are in this application specifically described one form and a modification which the invention may assume in practice, it will be understood that this form and modification of the same are shown for purposes of illustration and that the invention may be further modified and embodied in various other forms without departing from its spirit or the scopeo-f the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. A rock drill bit of the impact type comprising a body having slots extending across the front face thereof in substantially right angular relation, hard metal inserts providing wear resisting cutting edges and secured in said slots with their inner ends spaced from the center of the bit, and a rigid, multi-armed spider arranged centrally of and secured to the bit body with the arms thereof received in said slots in alignment with said inserts and with which the latter abut positively to prevent endwise displacement of said inserts in said slots toward the bit center.

2. A rock drill bit of the impact type comprising a body having slots cut in the front face thereof completely across the bit in substantially right angular relation and a central cleansing fiuid passage, hard metal inserts providing wear resisting cutting edges and secured by brazing in said slots with their inner ends spaced from the center of the bit, and a rigid, multi-armed spider arranged centrally of and secured by brazing to the bit body with the arms thereof received in said slots in alignment with said inserts and with which the latter abut positively to prevent endwise displacement of said inserts in said slots toward the bit center.

3. A rock drill bit of the impact type comprising a body having slots cut in the front face thereof in substantially right angular relation completely across the bit and a central cleansing fluid passage, hard metal inserts providing wear resisting cutting edges and secured by brazing in said slots with their inner ends spaced from the center of the bit, and a separate, rigid, cruciform shaped abutment member arranged centrally of and secured by brazing to the bit body with the arms thereof received in said slots .and secured therein by brazing, said arms being disposed in alignment with said inserts to provide rigid abutments for the inner ends of the latter positively to prevent endwise displacement of said inserts in said slots toward the bit center.

4. A rock drill bit of the impact type comprising a body having slots cut in the front face thereof in substantially right angular relation completely across the bit and a central cleansing fiuid passage, hard metal inserts providing wear resisting cutting edges and secured by brazing in .said slots with their inner ends spaced from the center of the bit, and a separate, rigid, cruciform shaped abutment member arranged centrally of and secured by brazing to the bit body l past said abutment member to the cutting face of the bit.

. v 5. A rock drill bit. of the impact type comprising a body having a central recess and a central cleansing fluid passage communicating with said recess, said body having diametric slots cut in substantially right angular relation in the front face thereof completely across the bit, hard metal inserts providing wear resisting cutting edges and secured by brazing in said slots with portions of their inner ends projecting slightly into said central recess but spaced from the center of the bit, and a rigid, multi-armed spider arranged centrally of and secured at the center of the bit body, said spider being disposed with its arms received in said slots and with its upper surface substantially flush with the bottom of said recess, said arms being secured by brazing in said slots and disposed in alignment with said inserts to provide rigid abutments for the inner ends of the inserts positively to prevent endwise displacement of said inserts in said slots toward the bit center.

6. A rock drill bit of the impact type comprising a body having a central recess and a central cleansing fluid passage communicating with said recess, said body having diametric slots cut in substantially right angular relation in the front face thereof completely across the bit, hard metal inserts providing wear resisting cutting edges and secured by brazing in said slots with portions of their inner ends projecting slightly into said central recess but spaced from the center of the bit, and a rigid, multi-armed spider arranged centrally of and secured at the center of the bit body, said spider being disposed with its arms received in said slots and with its upper surface substantially flush with the bottom of said recess, said arms being secured by brazing in said slots and disposed in alignment with said inserts to provide rigid abutments for the inner ends of the inserts positively to prevent endwise displacement of said inserts in said slots toward the bit center, said spider having spaces between the arms thereof to provide free flow of cleansing fluid from said passage past said spider to said central recess.

'7. A rock drill bit of the impact type comprising a body having a diametric slot cut in its front face completely across the bit and a central cleansing fluid supply passage, hard metal inserts providing wear resisting cutting edges and secured in said slot by brazing at the opposite sides of the bit center with the inner ends of said inserts spaced from the bit center, and a separate, rigid, abutment element secured at the central portion of said bit with rigid portions secured in said slot with which the inner ends of said inserts abut positively to prevent endwise displacement of said inserts in said slot toward the bit center, said abutment element extending across the front end of said passage and of less width than said passage to provide lateral spaces for free flow of cleansing fluid from said passage past said abutment element to the cutting face of the bit.

8. A rock drill bit of the impact type compris ing a body having a central recess and slots extending from said recess to the periphery of the bit, hard metal inserts providing wear-resisting cutting edges and secured in said slots with their inner ends spaced from the center of the bit, and a rigid, multi-armed spider arranged in said recess centrally of the bit body and secured to the bit body with the arms of said spider received in said slots in alignment with said inserts and with which arms said inserts abut positively to prevent endwise displacement of said inserts in said slots toward the bit center.

ROBERT T. EAKIN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,022,194 Galvin Nov. 26, 1935 2,252,745 Williams Aug. 19, 1941 FOREIGN PATENTS Number Country Date 5,778 Great Britain Mar. 14, 1908 

